Such rocker arms are known from the state of the art; they are generally used as transmission elements in three types of engine controls, for push-rod engines with the cam shaft on the bottom, for an overhead cam shaft with the rocker arm as the direct transmission element between the cam shaft and the valve, and with tappet control, where the rocker arm and the tappet form the transmission mechanism. In this connection, mechanical valve adjustment for sheet-metal rocker arms is performed at the ball socket bearing, or at the rocker arm end, by means of adjustment screws or eccentric elements. In this connection, the change in the lever ratio has a disadvantageous effect. Furthermore, the thumb rest on the valve-side end of the rocker arm, which is used in the state of the art, has disadvantageous friction values, resulting in high wear friction and wear of the valve guide, because of the lateral force of the valve shaft. In addition, in the case of the known, deep-drawn rocker arms, they must be additionally secured to prevent them from twisting, in order to stabilize the rocker arms around its longitudinal axis. Such a rocker arm is described in DE 4024446 A1. Here, the rocker arm is mounted on a roller bearing, to keep it from twisting.
The present invention is therefore based on the problem (task) of improving the known, deep-drawn rocker arm known from the state of the art, and significantly reducing the valve guide wear and, at the same time, simplifying production and making it more cost-effective.
This task is accomplished, according to the invention, by means of a rocker arm made from a punched, deep drawn and subsequently heat treated, deep drawn sheet metal, and a roller element is mounted in slits inside parts which are open in the direction of a valve shaft.
In accordance with the invention, the rocker arm is structured in such a way that it has opposite side parts, between which a roller element is held so as to rotate.
Because of the low rolling friction on the valve shaft, its lateral force on the valve guide is also reduced, and therefore the valve guide wear is significantly reduced. Furthermore, the rocker arm according to the invention can be produced very cost-effectively, since only deep-drawing and punching processes, but no cutting work, are required. Heat treatment of the deep-drawn part subsequently takes place by means of nitriding, carbonizing, or case-hardening. In the present case, valve adjustment takes place at the ball socket bearing, by means of a ball nut and a counter-bolt or counter-worm screw. Instead of the ball nut, a semi-cylindrical or cylindrical guide stone with a counter-nut can also be used. Furthermore, the invention provides that the roller element is mounted in slits in the side parts, which are open in the direction of the valve shaft. As a result, simple assembly is ensured, and additional locking of the roller element in the bearing is unnecessary, since the roller element is held in place in the bearing by the counter-pressure of the valve tappet.
Furthermore, it is advantageous that the roller element is loosely held in the slits. This ensures that it rotates easily, on the one hand, and that it is easy to assemble, on the other hand.
A highly advantageous embodiment of the invention provides that side guide parts are provided in the two end regions of the roller element, and that these extend beyond the valve shaft laterally. This prevents twisting of the rocker arm on the valve shaft, in surprisingly simple manner, i.e. the valve shaft is stabilized around its longitudinal axis. In this connection, the side guide parts can be connected in one piece with the roller element, i.e. project beyond its diameter, or can be separate components. It is important here that the rocker movement of the rocker arm and the rolling movement of the roller element are not hampered.
Furthermore, an advantageous embodiment of the present invention provides that the side guide parts are arranged between the side parts and the roller element. This fixes the rocker arm and the valve shaft in place, relative to one another, via the side guide parts.
Another advantageous embodiment provides that the side parts are guide disks. This makes it possible to use mass-produced parts, which are inexpensively available.
Finally, it is a highly advantageous embodiment of the present invention if the roller element has offset bearing ends. This reduces the number of components and makes assembly and storage costs more advantageous.
The present invention will be explained in greater detail below, on the basis of an exemplary embodiment, in connection with the attached figures. These show: